Our former CTO (now "consultant") at some point warned his replacement about not virtualizing database servers, specifically our PgSQL database servers, but rather run them as actual, physical servers. The problem with this is that we are rapidly running out of physical space in our racks and capacity on our main database server.
He offered little more than vague musings on I/O speed; and although I don't have any specific reason to mistrust his judgement on this matter, it would be good to know:
Is there a real reason for this recommendation (and if so, what?), or is it mere superstition on his part?